Television broadcast systems, such as satellite television broadcast systems, permeate virtually every aspect of daily life in modern society. As a result, such television broadcast systems have become an important, and in some cases, necessary fixture of modern living. Today, many television service providers, such as satellite service providers, provide programming from numerous sources. These sources include national, local, and specialty sources. A problem facing such television service providers is harmonizing audio levels provided by the various television programming sources. Without such harmonization, audio issues manifest themselves in several ways. For example, different channels can have different base audio levels. This can be quite disconcerting to a user who must constantly adjust channel volume when switching between channels whose sources provide different base audio levels.
A challenge facing television service providers attempting to address this problem is the lack meaningful audio monitoring systems for conventional television broadcast systems. Typically, conventional television broadcast system monitoring employs a hardware device such as the Dolby® LM100 (“LM100”) to determine audio loudness at a particular time. Using the ITU-R BS 1770 standard for audio loudness, the LM100 displays audio loudness in units of LKFS, where 1 LKFS equals 1 dB.
However, hardware devices such as the LM 100 are of limited utility for monitoring and controlling audio levels to efficiently address audio harmonization issues. For example, the LM100 can monitor only one channel in a television broadcast system at any given time. Even monitoring a single channel is problematic because two devices are required per channel - one to monitor source input for the channel, and one to monitor broadcast output for the channel. Trying to overcome this problem using a sufficient number of hardware monitoring devices in a television broadcast system presents its own set of problems, primarily in the enormous cost that would be associated with the effort. By way of example, in a satellite system, channels are assigned to transports that corresponding to satellite transponders used to broadcast television programming to subscribers. Each transport can support up to 15 television channels. Thus, up to 30 LM 100s would be required to fully monitor a particular transport. Monitoring audio levels in modern satellite television systems having hundreds of transports carrying thousands of channels would require thousands of LM 100s. Clearly, this is impractical from both a cost and logistics viewpoint. Consequently, typical convention systems monitor only a few of the available channels in a television broadcast system.
Another limitation of conventional hardware devices is that generally they do not provide historical perspectives of audio loudness and dialnorm. For example, the LM 100 provides only long term averages, for example, average loudness over a week. As a result, it is difficult or impossible to determine trends in audio loudness over time. Moreover, conventional hardware television broadcast system monitoring systems typically provide statistics on-site only. As a result, in conventional systems, only broadcast operations personnel at a specific broadcast location can access the measurements. This makes it difficult or impossible to provide the required data to remote personnel whom might be better able to solve audio loudness issues.
Further, in modern satellite systems, data to be broadcast is generally processed by a transport processing system. Prior transport processing systems process have limited capabilities to monitor video and audio data carried by channels in a particular transport, for example, a satellite transponder. While prior transport processing systems provide some data concerning audio in each channel of the transport, they do not provide historical data collection. As a result, prior transport processing systems provide only an estimate of audio level for a particular channel at a particular time. Moreover, the audio estimate provided by prior transport processing systems is not very accurate.
Industry recommendations for audio loudness have been promulgated. For example, the ATSC Recommended Practice: Technique for Establishing and Maintaining Loudness for Digital Television, Document A/85:2009 (Nov. 4, 2009) (“ATSC A/85”), which is incorporated herein by reference in its entirety, provides guidelines for audio loudness for standard definition (“SD”) and high definition (“HD”) television.
However, the ATSC A/85 contains differences in the recommendations of audio loudness for audio associated with SD services (MPEG-1, layer II audio) and audio associated with high definition HD services (AC-3 audio). More specifically, the ATSC A/85 recommends a −24 dB target audio loudness for MPEG-1, layer II audio (SD) channels and a −31 dB target audio loudness for AC-3 audio (HD) channels. Thus, even where sources providers follow the ATSC A/85 recommendations, SD channels are typically 7 dB louder than HD channels. Thus, a subscriber switching from an SD channel to an HD channel or vice versa will likely notice a large volume difference, despite not adjusting the volume his or herself
Even more problematic is that not all source providers follow the ATSC A/85 recommendations. As a result, large audio loudness differences in audio data provided by disparate source providers are often observed. This can result in wide audio loudness variations even when switching from one HD channel to another HD channel or from one SD channel to another SD channel or when switching from local service providers to national service providers, etc.
For example, weekly averages of AC-3 CONUS (Continental US) audio loudness have been observed ranging from −38 dB to −22 dB; weekly averages of SD Legacy CONUS audio loudness have been observed ranging from −32 dB to −16 dB; weekly averages of AC-3 SLiL (Spotbeam local-into-local) have been observed ranging from −40 dB to −12 dB; and weekly averages of SD Legacy SLiL have been observed ranging from −32 dB to −4 dB. Even though average loudness may not vary that much from the target recommended loudness levels, the wide ranges can produce extremely annoying effects for subscribers. For example, switching from a station with an average loudness of −32 dB to a station with an average loudness of −4 dB would likely startle a subscriber due to the large volume increase, and could possibly damage equipment, for example, damage a speaker.
The disconcerting effects associated with varying audio loudness can manifest themselves in a number of situations. For example, a subscriber may be watching an SD channel, start recording an HD channel, and then decide to watch the HD channel. Because the volume of the HD channel will likely be too low if both the SD and HD sources adhere to the ATSC A/85 recommendations, the subscriber will increase the volume to view the HD channel. When HD channel recording stops either because the program has completed or the subscriber terminates the recording early, the television may revert back to the SD channel. In such a case, the volume will rise dramatically due to the 7 dB target loudness difference between the HD and SD channels. Not only might the subscriber be startled, but he or she will have to lower the volume. This constant volume adjustment can be frustrating to subscribers, in particular, because they are not doing anything to change volume.
In another example, television service providers may receive audio from a source in one format but desire recode the received audio in another format for broadcast. For example, for some channels, a service provider may receive audio in an AC-3 audio format, but desire to recode it in an MPEG-1, layer II audio format. This requires first decoding the input format. With respect to AC-3, for example, there are two modes of decoding—RF mode and line mode. In line mode decoding, no gain offset applied. However, when performing RF mode decoding, the decoder applies an 11 dB increase to the audio to address signal-to-noise issues. As a result, even more acute sound differences can result when switching between SD and HD channels than described above with respect to the 7 dB difference, again with the annoying requirement to adjust volume, not to mention the startling effect an 11 dB volume increase may have.
These changes in loudness levels can be disconcerting and annoying to subscribers, particularly where they have not performed any action to change audio loudness. In many cases, the audio loudness change causes subscribers to believe there is a malfunction with their systems. As a result, subscriber calls and complaints to service providers may very likely increase. Without proper tools to monitor and control audio loudness, inefficiencies in terms of wasted technician hours, call center hours, and the like, will likely result in increased cost, and lower subscriber satisfaction.